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package CONTABILIDAD_MODELO;

/**
 *
 * @author equipo_4
 */
public class Verhoeff {
 
 
    // The multiplication table
    static int[][] d  = new int[][]
    {
        {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, 
        {1, 2, 3, 4, 0, 6, 7, 8, 9, 5}, 
        {2, 3, 4, 0, 1, 7, 8, 9, 5, 6}, 
        {3, 4, 0, 1, 2, 8, 9, 5, 6, 7}, 
        {4, 0, 1, 2, 3, 9, 5, 6, 7, 8}, 
        {5, 9, 8, 7, 6, 0, 4, 3, 2, 1}, 
        {6, 5, 9, 8, 7, 1, 0, 4, 3, 2}, 
        {7, 6, 5, 9, 8, 2, 1, 0, 4, 3}, 
        {8, 7, 6, 5, 9, 3, 2, 1, 0, 4}, 
        {9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
    };
 
    // The permutation table
    static int[][] p = new int[][]
    {
        {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, 
        {1, 5, 7, 6, 2, 8, 3, 0, 9, 4}, 
        {5, 8, 0, 3, 7, 9, 6, 1, 4, 2}, 
        {8, 9, 1, 6, 0, 4, 3, 5, 2, 7}, 
        {9, 4, 5, 3, 1, 2, 6, 8, 7, 0}, 
        {4, 2, 8, 6, 5, 7, 3, 9, 0, 1}, 
        {2, 7, 9, 3, 8, 0, 6, 4, 1, 5}, 
        {7, 0, 4, 6, 9, 1, 3, 2, 5, 8}
    };
 
    // The inverse table
    static int[] inv = {0, 4, 3, 2, 1, 5, 6, 7, 8, 9};
 
 
    /* 
     * For a given number generates a Verhoeff digit
     * 
     */
	public static String generateVerhoeff(String num){
 
		int c = 0;
		int[] myArray = StringToReversedIntArray(num);
 
		for(int i = 0; i < myArray.length; i++)
		{
			c = d[c][p[((i + 1) % 8)] [myArray[i]]];
		}
 
		return Integer.toString(inv[c]);
	}
 
 
	/*
	 * Validates that an entered number is Verhoeff compliant.
	 * NB: Make sure the check digit is the last one.
	 */
	public static boolean validateVerhoeff(String num){
 
        	int c = 0;
        	int[] myArray = StringToReversedIntArray(num);
 
        	for (int i = 0; i < myArray.length; i++)
        	{
        		c = d[c][p[(i % 8)][myArray[i]]];
        	}
 
		return (c == 0);
	}
 
 
 
	/*
	 * Converts a string to a reversed integer array.
	 */
	private static int[] StringToReversedIntArray(String num){
 
		int[] myArray = new int[num.length()];
 
		for(int i = 0; i < num.length(); i++)
		{
			myArray[i] = Integer.parseInt(num.substring(i, i + 1));					
		}
 
		myArray = Reverse(myArray);
 
		return myArray;
 
	}
 
	/*
	 * Reverses an int array
	 */
	private static int[] Reverse(int[] myArray)
	{
		int[] reversed = new int[myArray.length];
 
		for(int i = 0; i < myArray.length ; i++)
		{
			reversed[i] = myArray[myArray.length - (i + 1)];			
		}
 
		return reversed;
	}
 
 
}
